In the field of photonics, optical fibers are used for the transmission of optical signals as well as for the linking of optical switches, waveguide grating devices, optical amplifiers, modules and the like. Optical transmission systems relying on photonics have been taking on greater importance, as optical signals are capable of carrying far larger amounts of information as compared to typical copper wire communication systems. For example, with the technology of Dense Wavelength Division Multiplexing (DWDM) and Demultiplexing it is possible to transmit multiple wavelengths in a single fiber, providing data capacities of 40 Gigabits per second and greater.
Optical networks which require DWDM equipment and other such devices demand multiple amounts of splicers and connectors. Splicing and connecting play a significant role in network cost and performance. Although mechanical splicing of optical fibers may be sufficient where there is no requirement for frequent connection and disconnection, connectors will be used in applications where flexibility for routing or reconfiguration is necessary or for connection of an end use device, such as a computer or other electronic device to a fiber or to other such devices. Current technologies for connectors or for splicing are time consuming and expensive, since they are difficult to miniaturize and to manipulate.
As poor connection between the ends of two optical fibers will lead to signal distortion and loss of strength, a number of approaches have been proposed for proper optical fiber connection which will provide a good signal conduction. One such approach is set out in our U.S. patent application No. 60/358,392, filed Feb. 22, 2002, titled “A Connector for Optic Fibers”. This application is incorporated herein by reference in its entirety.
In our aforesaid application, we propose a connector for connecting the ends of two optical fibers by abutment, wherein the connector is divided into a plurality of fingers that extend longitudinally at each end and a fiber conduit extending from the first end to the second end. Such a connector is manufactured of a shape memory material such as polymer or a metal alloy. In general, such materials when deformed from a rest condition by any suitable means, such as by the application of heat, will then be biased to return to a rest condition when the cause of deformation is removed. As set out in our aforementioned application, an example of such a material is any material that deforms within its elastic limit under mechanical deformation. Another example would be any material that expands suitably due to a temperature increase, and then returns to its initial rest condition when the temperature is reduced to the initial temperature
An example of such an above material would be a shape memory alloy (SMA). Examples concerning activation of the shape memory element in a SMA include D. E. Muntges et. al., Proceedings of SPIE volume 4327 (2001), pages 193-200 and Byong-Ho Park et. al., Proceedings of SPIE volume 4327 (2001), pages 79-87. Miniaturized components, of SMA may be manufactured by laser radiation processing. See for example H. Haferkamp et. al., Laser Zentrum Hannover e.v., Hannover, Germany. All of the above references are incorporated herein by reference.
To connect the ends of two optical fibers using our connector, the connector must be first deformed in any, suitable way, such as by heat or the application of a compressive force along its longitudinal access. For example, the connector may be heated to a sufficient temperature so that the conduit through the connector for passage of the optical fiber ends is enlarged, sufficiently to permit passage of the ends of the optical fibers. In this condition, the ends of the optical fibers are inserted into the conduit. An optical gel may also be applied, which would be substantially of the same index of refraction as the optical fibers to assure uniform optical properties across the connection between the fibers.
Once the optical fibers ends are fully inserted into the connector, and the respective ends abut, the connector may then be cooled and allowed to return to an initial size. On cooling, the connector will then tend to exert a controlled compressive force on the optic fibers strong enough to retain the optic fibers in an abutment position but small enough not to damage the optic fibers by compression.
SMA technology is particularly suited to optical fiber connection, as it offers mechanical precision in the order of +/−0.01 micron, which is 400 times more precise than current connector technology.
Use of such an optical fiber connector as described above is however not totally satisfactory as during the step of cooling the connector to allow it to return to its rest condition, there may be a tendency for the connector to push the ends of the optical fibers apart slightly. This makes it necessary during the operation of connecting optical fiber ends to include an additional step of restraining the optical fibers in a fixed position during the step where the connector returns to its original size, to prevent the optic fibers from being moved apart on the cooling of the connector. Accordingly, some form of fixed clamping is required, of the sheath that typically covers and protects an optical fiber or bundle of such fibers to prevent axial movement of the optic fibers being connected.
Such a step is cumbersome to the easy and quick connection of optical fibers using an aforesaid connector. This typically requires the use of certain operational skill by a technician that is carrying out the operation and is a hindrance to the quick and easy connection of optical fibers, to be used in any context where fibers are to be connected, including and in particular, in the context of a “last mile” connection where incoming fibers from an optical network are to be connected to an end use device, such as in a home, office, workplace and like environment.
An example of a detachable/demountable connector for coupling optical fibers is described in EP 373 340 to Rott et al. In order to connect the fibers, the end portion of each fiber is fitted into a connector element that has a bush that encloses three short rods of circular cross section. The connector element is also comprised of a cage and a clamp. These rods form a centralizing device for the end of the wave-guide. Each half of the coupling has an outer bush that receives the inner bush of each connector element. The coupling aligns the fibers with one another. Furthermore, the transition from the “connection stage” to the “connected stage” is achieved by axial interlocking. However, this connector is cumbersome and difficult to use and does not allow for easy connection of optical fibers being connected since it comprises multiple pieces, such as a bush, a cage and a clamp.
Accordingly, although a SMA connector as described in our U.S. patent application No. 60/358,392 provides an improved means for connecting optical fibers, there is a continuing need for an optical fiber connector assembly that is simple and quick to install and use, and to maintain good signal conduction between optical fibers, and to be used in any context where fibers of an optical network are to be connected, including, and in particular for a connection to be made and provided at the end use location.